Mailing-List: contact user-help@couchdb.apache.org; run by ezmlm
Precedence: bulk
Reply-To: user@couchdb.apache.org
Received-SPF: pass (nike.apache.org: domain of jens@couchbase.com designates
 206.225.164.30 as permitted sender)
From: Jens Alfke <jens@couchbase.com>
To: "user@couchdb.apache.org" <user@couchdb.apache.org>
Date: Wed, 9 May 2012 14:31:35 -0700
Subject: Re: include_docs with _all_docs
Thread-Topic: include_docs with _all_docs
Thread-Index: Ac0uKxyHC/MkxMi7Ra+6im4E8198jg==
Message-ID: <7CC02CFB-C515-478C-813C-274859EE5D4B@couchbase.com>
References: 
 <CAHKsR692SAqfg3aPvOJyp+HftDQtA5Vf8PNLG+OVk2p9z_9RDw@mail.gmail.com>
 <b24ecbb5fe9bb8bcd5beaf3d5ecc251f.squirrel@secure61.inmotionhosting.com>
 <CABvT1DFaw6RwK4ZX8WVk109o3Tt_5XWCNJ9bydHR=_d0b6CrPw@mail.gmail.com>
 <7caa2578e04507ec25f97df01e5d66ab.squirrel@secure61.inmotionhosting.com>
 <FE5952D2-D2ED-4D21-BB26-4E6206317931@couchbase.com>
 <2ba5948b99a136aebad13e1cfcd8b525.squirrel@secure61.inmotionhosting.com>
In-Reply-To: 
 <2ba5948b99a136aebad13e1cfcd8b525.squirrel@secure61.inmotionhosting.com>
Accept-Language: en-US
Content-Language: en-US
acceptlanguage: en-US
Content-Type: text/plain; charset="Windows-1252"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0


On May 9, 2012, at 1:21 PM, <dan@danmyersconsulting.com> <dan@danmyersconsu=
lting.com> wrote:

> 1. If I don't know what attributes exist in the database there is no way
> to write a query about those attributes on documents.

Usually you know something about the schema of the data in a database befor=
e writing code to operate on it. CouchDB doesn=92t enforce any schema, but =
you=92d generally define what properties you put in documents beforehand.

What kind of program are you writing? I=92m not an RDBMS guru but I=92ve wr=
itten some apps that use SQL databases, and I haven=92t had to introspect t=
he metadata of the table columns. I=92ve defined my tables and then written=
 my queries using the columns I defined.

Keep in mind that, to some degree, it doesn=92t make sense to ask =91what a=
ttributes exist in the database=92 because every document could have a diff=
erent set of attributes. It=92s very unlikely but possible. CouchDB has not=
hing comparable to =91columns=92 in SQL; every document is an independent b=
ag of JSON.

> 2. If I create my own attribute of a document which stores metadata for
> that document it works but if that metadata attribute isn't a required
> attribute for all docs then how can I enforce the collection of metadata
> which supports #1 above?

You can add a validation function to a design document that will enforce th=
e presence of that attribute, or any structure you want your documents to h=
ave.

> 3. I can create a attribute that would provide a description of a
> document, e.g.#2 above (aka metadata) but how do I create an attribute of
> a document attribute? (e.g. an description for a document attribute calle=
d
> "telephone", which is now an attribute of an attribute or meta-attribute)=
?

I really have no idea where you=92re going with this. It=92s awfully abstra=
ct. What are you trying to accomplish?

=97Jens=